The field of the invention is automated workpiece processing systems, used for processing workpieces, such as semiconductor wafers, hard disk media, substrates, optical materials, as well as other workpieces formed from a substrate upon which microelectronic circuits or components, data storage elements or layers, and/or micro-mechanical elements are or can be formed. These and similar materials generally requiring very low levels of contamination, are collectively referred to here as xe2x80x9cwafersxe2x80x9d or xe2x80x9cworkpiecesxe2x80x9d.
Computers, televisions, telephones and other electronic product contain large numbers of essential electronic semiconductor devices. To produce electronic products, hundreds or thousands of semiconductor devices are manufactured in a very small space, using lithography techniques on semiconductor substrates, such as on silicon wafers or other substrates. Due to the extremely small dimensions involved in manufacturing semiconductor devices, contaminants on the semiconductor substrate material, such as particles of dust, dirt, paint, metal, etc. lead to defects in the end products.
Existing automated semiconductor processing system use robots, carriers, rotors, and other devices, to move and process wafers. Many automated semiconductor processing systems use centrifugal wafer processors, which spin the wafers in a rotor at high speed, while spraying or otherwise applying process fluids and/or gases onto the wafers. The rotors typically hold a batch of wafers in a parallel array. Other types of processors have a fixed or rotating workpiece supports holding workpieces within a chamber. Process fluids, such as liquids, gases or vapors are introduced into the chamber to process the workpieces. Typically, automated semiconductor processing system have robots which move workpieces between different stations or locations, as described, for example, in U.S. Pat. Nos. 5,544,421 and 5,664,337, incorporated herein by reference. In some systems the robots handle the workpieces directly, generally by picking them up or holding the workpiece at the edges of the workpiece. Other systems have robots which handle workpieces using suction cups or similar devices on the top or bottom surface of the workpiece.
These types of robots and handling techniques have certain disadvantages. Micro-electronic devices or other components necessary in the ultimate product manufactured from the workpiece (e.g., micro-electronic circuits) are created on the front and/or back surfaces of the workpiece. Consequently, handling the workpiece on these surfaces can lead to defects and reduced yield in the manufacturing process. As a result, handling workpieces by their edges is preferred, because no components are formed at the edges. However, handling workpieces at the edges requires precise positioning of the robot for pick up and placement of a workpiece. In addition, as the workpieces are typically fragile, they must be handled gently by the robot. Rubbing or scraping of a workpiece, or rough handling, may also result in damage or the creation of particles which may settle on a workpiece, resulting in defects.
Robots which handle workpieces by their edges have been used, with varying degrees of success. However, these robots require precise pre-positioning, before making contact with the workpiece. While the added time required for pre-positioning a robot for a single workpiece pick up operation may be relatively little, the added time for this positioning and movement, over hundreds or thousands of workpiece pick up cycles, becomes substantial.
Accordingly, an improved robot and workpiece handling methods are needed for use in an automated workpiece processing system.
A workpiece handling robot has now been invented for picking up and handling workpieces by their edges in a quick and direct way, and without the need for extensive time-consuming precise alignment or pre-positioning of the robot relative to the workpiece. In a first aspect, an automated processing system has a robot at a transfer station. The robot withdraws workpieces from a container at a docking station and moves the workpieces to a carrier. The robot has an end effector or hand having first and second arms or tines. Each arm has a workpiece contact. The robot is moved so that the workpiece is between the arms. The arms are then brought together, with the workpiece contacts engaging the edges of the workpiece. The arms preferably remain parallel at all times. The contacts on the arms preferably move linearly to contact and pick up the workpiece. Extensive robot pre-positioning movements, to align the robot with the workpiece, are avoided. In addition, the workpiece contacts preferably contact the workpiece edges nearly simultaneously. This reduces or avoids sliding movement of the workpiece, which can cause damage or contamination to the workpiece.
In a second aspect, the first and second arms are driven by a linkage which moves the arms simultaneously in equal and opposite directions. This provides for automatic precise four-point contact between the robot and the workpiece, resulting in simplified and expedited handling.
In a third aspect, an actuator drives the linkage moving the first and second arms. The limited amount of force exerted by the actuator on the linkage correspondingly limits the force which the workpiece contacts on the arms may exert on the workpiece. As a result, gentle handling of the workpiece is automatically provided.
In a fourth aspect, sensors are provided on the robot, to detect whether the robot has successfully picked up a workpiece. This feature reduces potential for damage to workpieces, by signaling the robot controller to stop or reverse robot movement, when appropriate.
Other advantageous features will also be shown and described. The invention resides as well in subcombinations of the components and methods described. It is an object of the invention to provide an improved robot for handling workpieces in an automated workpiece processing system.